Margaret Judge

CU Boulder, Fall 2002

The purpose of this experiment was to determine how the respiration rates of poikilotherms¹ and homeotherms² are affected by changes in temperature. Homeotherms maintain a constant internal body temperature, even when they are subjected to fluctuating environmental temperatures. Therefore, it was expected that their respiration rates would increase when exposed to cold temperatures. The internal body temperature of poikilotherms changes in response to their surrounding temperatures. Thus, it was hypothesized that their respiration rates would decrease when exposed to cold temperatures.

To record respirations rates, a gas sensor probe was used to measure the amount of Carbon Dioxide (CO₂ ), which is an output of respiration, in a gas chamber. Twenty house crickets (Acheta domestica) were used to represent poikilotherms, and two dwarf hamsters (Phodopus cambelli,) were used to represent homeotherms. The crickets were first placed in an air-tight chamber, and the amount of CO₂ present in the chamber was recorded over 4-minutes³. Three trials were conducted, one at a warm temperature (28° Celsius), one at a cold temperature (15° Celsius), and one at room temperature (23°Celsius)⁴. Following the cricket respiration recordings, the hamsters were tested under the same conditions.

The results indicated that respiration rates for crickets and hamsters were affected differently when subjected to warm and cold temperatures. The respiration rate of hamsters increased slightly in cold air, while the respiration rate of crickets decreased dramatically in cold air.

The results of this experiment are consistent with the hypothesis, but only marginally (p = 0.045). This moderately significant data set showed that the hamster respiration rates in cold air were only slightly more than their respiration rates in warm air. A potential problem was with the amount of time the hamsters were subjected to varying temperatures. There may not have been enough time for their metabolic rate to increase, and thus create more measurable CO₂. Upon making behavioral observations of the hamsters, it actually appeared they preferred the CO₂-rich environments. This could imply that the hamsters have become adapted to small, enclosed areas having low amounts of CO₂, which could mean they do not perform as much respiration. This would skew the results of the affect temperature alone had on the hamsters’ respiration values. Moreover, the amount of CO₂ in the chamber was consistently five times more than the level of CO₂ when crickets were the occupants. Another potential problem was with the equipment. A different type of CO₂ gas sensor should have been used for live animals. This would have allowed for longer session times.

Footnotes:

1. poikilotherms = organisms whose internal body temperature changes with temperature changes in the external environment
2. homeotherms = organisms that attempt to maintain their body temperatures within a range most suitable for optimal biological activity
3. the organisms (crickets and hamsters) were only kept in a container for a time period of four minutes in order to ensure their safety
4. respiration measurements taken at room temperature were used as a control